1. Cut the tuna steaks into long rectangles, resembling the shape and size of hot dogs and place in a glass dish or zip-top plastic bag. 2. In a medium bowl, combine the lime juice, white vinegar, soy sauce, brown sugar, vegetable and sesame oils and cayenne. Remove 1/4 cup of the dressing and pour over the tuna steaks. Marinate tuna steaks, refrigerated, for 30 minutes. 3. Meanwhile, in a large bowl combine the remaining dressing with the coleslaw, julienned peppers and green onions. Cover and refrigerate. 4. To sear the steaks, heat a saute pan over medium-high heat. Remove the tuna pieces from the marinade, shaking off excess and add them to the hot pan. Sear the tuna 2 minutes per side for medium-rare, or until desired doneness is reached. 5. Prepare the wasabi mayonnaise by combining the mayonnaise with the wasabi powder, if desired. 6. Split hot dog buns and fill with some of the coleslaw and the hot tuna "dogs". Serve the wasabi mayonnaise on the side as a condiment.